The present disclosure relates to an apparatus for measuring spectral and spatial information on a printing press.
In the printing industry, a desired image is repeatedly printed on a continuous web or substrate such as paper. In a typical printing process, the continuous web is slit in the longitudinal direction (the direction of web movement) to produce a plurality of continuous ribbons. The ribbons are aligned one on top of the other, folded longitudinally, and then cut laterally to produce a plurality of multi-page, approximately page-length segments, each of which is termed a “signature”. The term signature also encompasses a single printed sheet that has or has not been folded.
To monitor the print quality on a signature, various methods may be used to measure the color quality of the printed signature. One method includes printing a colorbar having multiple color patches of different known colors and intensities such that the color quality of the colorbar can be measured and compared to a standard, the colorbar being representative of the color quality of the printed signature. By so doing, the color quality of the printed signature may be measured by utilizing an image processing apparatus (e.g., a camera) to acquire an image of a single point of the printed colorbar. Current image processing apparatus systems for measuring the color quality may utilize a single camera, such as a charge-coupled device (“CCD”) color camera having red, green, and blue channels (i.e., an RGB camera).
It may also be desired to provide an image processing device that can take color measurements at a high rate of speed. The ability to take color measurements at a high rate of speed would allow for more direct measurement of the printed image (i.e., the ability to measure color in the work in addition to the colorbar), would make the control system respond faster to color errors, and would assist in locating a desired place on the signature with a searching algorithm for additional measurements.